webadmin: NPE on new/edit pool

If no DC was up, the new/edit dialog pool failed on NPE.

Similar issue was also on the new/edit VM - fixed the same way.

Change-Id: Ia94ec0d89f3304597cce5187a1f449dc5fbfd6ed
Signed-off-by: Tomas Jelinek <tjelinek@redhat.com>